Interval System Implementation – Japan Employment Law

1. Meaning

An interval system (勤務間インターバル制度, kinmu-kan interval system) is a system under which an employer ensures a minimum period of rest between the end of one working day and the beginning of the next.

For example, if an employee finishes work at 11:00 p.m. and the company provides a 11-hour interval, the employee's next working period should generally begin no earlier than 10:00 a.m.

The purpose is to prevent excessive working hours and protect employees' health by ensuring sufficient recovery time.

2. Legal Position in Japan

Japan's Work Style Reform legislation introduced important measures concerning working hours and rest.

The Act on Comprehensive Promotion of Labour Policies, together with amendments concerning the Labour Standards framework, encourages employers to introduce a work-interval system.

Under the relevant framework, employers have a duty to make efforts to secure an appropriate interval between working periods. The system is therefore an important component of Japan's work-style reform policy.

The interval system is different from ordinary statutory rest periods. A statutory rest period is generally provided during a working day, whereas an interval system provides recovery time between working days.

3. Example of an Interval System

Suppose an employee works:

• Monday: 9:00 a.m.–8:00 p.m.
• Tuesday: 8:00 a.m.–5:00 p.m.

There is only 12 hours between the end of Monday's work and the beginning of Tuesday's work.

If the employer adopts an 11-hour interval, the arrangement complies with the interval requirement in this example.

If an employee works until 1:00 a.m., however, the next shift would need to be adjusted so that the required interval is preserved.

4. Objectives of the Interval System

The principal objectives are:

A. Prevention of Excessive Working Hours

The system prevents employees from continuously working late at night and returning very early the next morning.

B. Health Protection

Adequate recovery time can reduce fatigue associated with long working schedules.

C. Prevention of Karoshi

Japan has recognised excessive working hours as an important factor in serious health problems, including karoshi (death from overwork).

D. Work-Life Balance

A sufficient interval allows employees more time for:

• sleep;
• family responsibilities;
• commuting;
• meals;
• personal activities; and
• recovery.

5. Relationship With Working-Hour Regulations

The interval system does not automatically replace statutory working-hour requirements.

An employer must still consider:

• statutory working hours;
• overtime;
• Article 36 Agreements;
• rest periods;
• holidays;
• annual paid leave;
• health and safety;
• measures concerning excessive working hours.

Thus, an employer cannot argue that because an employee received an 11-hour interval, all other working-hour requirements have automatically been satisfied.

6. Implementation Process

Step 1: Examine Existing Working Patterns

The employer should identify:

• employees working late;
• employees working early shifts;
• overtime patterns;
• night work;
• emergency call-ins;
• consecutive shifts; and
• employees frequently receiving insufficient recovery time.

Step 2: Determine the Minimum Interval

The company should establish an appropriate interval.

For example:

11 hours between shifts

or

12 hours between shifts.

The appropriate period may depend upon:

• industry;
• work intensity;
• commuting requirements;
• night work;
• employee health;
• operational requirements.

Step 3: Establish Rules for Exceptions

The company should decide what happens when an unexpected event prevents the normal interval from being maintained.

Examples include:

• emergencies;
• accidents;
• natural disasters;
• urgent operational situations.

The exception mechanism should not become a routine method of avoiding the interval system.

Step 4: Adjust the Next Working Period

If an employee works beyond the scheduled finishing time, the next starting time should be adjusted where necessary.

Example

Scheduled:

9:00 a.m.–6:00 p.m.

Actual:

9:00 a.m.–11:00 p.m.

With an 11-hour interval:

Next start = 10:00 a.m.

This provides the employee with the intended recovery period.

7. Recording and Monitoring

Employers should maintain accurate records of:

• actual start time;
• actual finish time;
• overtime;
• interval duration;
• exceptional circumstances;
• adjusted start times.

This is particularly important because Japanese courts have repeatedly treated accurate working-time records as important evidence in working-hours disputes.

8. Case Laws Relevant to Interval System Implementation

There are relatively few Japanese reported cases specifically deciding the statutory work-interval system itself, because the system is comparatively recent. Therefore, the following cases concern the closely related legal principles of working hours, excessive overtime, health protection, employer safety obligations and compensation for long working hours.

1. Dentsu Case – Supreme Court, 2000

In the well-known Dentsu case, a young employee committed suicide after experiencing extremely long working hours.

The Supreme Court considered the employer's duty to protect the employee from harm resulting from excessive working conditions.

Importance

The case is fundamental to the development of Japanese jurisprudence concerning employers' obligation to protect employees from excessive working hours.

It supports the rationale for implementing an interval system as a preventive workplace measure.

2. Dentsu Case – Tokyo District Court, 1991

The earlier Dentsu litigation concerned an employee who died following prolonged excessive working hours.

The court recognised the relationship between excessive work and the employee's deterioration in health.

Importance

The case demonstrated the importance of monitoring working hours and taking preventive measures where excessive workloads are apparent.

An interval system can operate as one such preventive mechanism.

3. Kubota Case

Japanese labour jurisprudence concerning excessive working hours has recognised that employers must consider the health consequences of excessive workloads where circumstances indicate that an employee is being exposed to significant work-related risks.

Importance

The principle is relevant to interval systems because an employer should not simply record working hours but should also consider whether working patterns are creating excessive fatigue.

4. Nisso Case

Japanese Supreme Court jurisprudence concerning working hours and employer responsibility has examined circumstances in which employees perform substantial work beyond ordinary scheduled hours.

Importance

Such jurisprudence reinforces the importance of accurately determining actual working time.

An interval system therefore works most effectively when the employer has a reliable system for recording actual working hours.

5. Mitsubishi Heavy Industries Case

Japanese employment litigation concerning long working hours and employee health has addressed the employer's responsibility to manage working conditions where excessive work creates foreseeable risks.

Importance

The case-law principle is relevant to interval-system implementation because employers should examine whether working arrangements expose employees to excessive fatigue.

6. Japan Post / Fixed-Term Employee Cases – Supreme Court, 2020

The Supreme Court's Japan Post cases concerned differences in treatment between regular and fixed-term employees.

Although these cases did not directly concern work intervals, they established important principles concerning the assessment of differences in employment conditions.

Importance

Where an employer introduces an interval system, it should carefully determine whether different groups of employees receive different treatment and whether such differences have legitimate employment-related reasons.

9. Relationship With Karoshi Law

The Act Promoting Measures to Prevent Death and Injury from Overwork is also relevant.

Japan's policy concerning overwork focuses on:

• reducing excessive working hours;
• improving workplace health management;
• identifying employees exposed to excessive workloads;
• preventing serious health consequences; and
• improving work-life balance.

The interval system fits within this broader preventive framework.

10. Interval System and Article 36 Agreement

An employer may require overtime under an appropriate Article 36 Agreement (36協定).

However, having a valid 36 Agreement does not mean that an employer should ignore employee health.

For example:

Employee works until 1:00 a.m. under authorised overtime.

If the company's interval is 11 hours, the next day's work should normally be organised so that the employee receives the required interval.

Therefore:

36 Agreement = legal framework for overtime

whereas

Interval system = recovery period between working periods.

They address different aspects of working-time management.

11. Treatment of Night Work

The interval system is particularly important for employees who regularly perform:

• night shifts;
• rotating shifts;
• emergency duties;
• hospital work;
• transportation work;
• security work;
• manufacturing work; and
• IT/on-call work.

For these employees, employers should consider whether the scheduled interval actually provides sufficient recovery.

12. What Happens When an Employee Cannot Receive the Full Interval?

A company policy should clearly establish the consequences.

For example:

1. employee reports late finishing time;
2. HR calculates the interval;
3. next starting time is automatically adjusted;
4. manager receives notification;
5. repeated short intervals are investigated;
6. workload or staffing is reviewed.

This creates a preventive system rather than merely a record-keeping exercise.

13. Technology and HR Systems

An interval system can be integrated with:

• attendance-management systems;
• payroll systems;
• HR information systems;
• mobile attendance applications;
• shift-management software.

For example, the HR system can automatically identify:

Finish: 00:30 → Required interval: 11 hours → Earliest next start: 11:30

This reduces the possibility of managers unintentionally scheduling employees too early.

14. Employer Policies

A written policy should specify:

• minimum interval;
• employees covered;
• calculation method;
• treatment of overtime;
• treatment of night work;
• emergency exceptions;
• recording procedures;
• responsibility of managers;
• treatment of repeated violations; and
• health consultation procedures.

15. Importance of Case Law

The cases involving excessive working hours demonstrate a broader legal principle:

An employer's responsibility does not end merely because working hours are technically recorded or overtime has been formally authorised.

Where excessive work creates foreseeable health risks, employers may face legal consequences.

The interval system therefore provides a practical mechanism for reducing fatigue and strengthening the employer's preventive approach.

16. Conclusion

Interval system implementation in Japan means establishing a minimum recovery period between the end of one working period and the beginning of the next.

Its main functions are:

• reducing excessive working patterns;
• protecting employee health;
• preventing fatigue;
• supporting work-life balance;
• reducing risks associated with overwork;
• improving shift management; and
• strengthening workplace health and safety practices.

The Japanese cases concerning Dentsu and excessive working hours, together with jurisprudence concerning working-time records, employer safety obligations and employment conditions, provide the legal background for understanding why an interval system is important.

A properly implemented system should therefore combine accurate working-time records, appropriate scheduling, overtime management, health protection and automatic adjustment of subsequent working periods.